The use of flexible resins with fabrics woven from high performance fibers to fabricate composite armor panels has been the subject of much research and many patents. The general consensus of this body of work is that the more flexible the resin system used in the fabrication of the composite, the better the ballistic properties of the resulting panel. In addition, adhesion of the resin to the ballistic yarn should be sufficiently poor that delamination in the composite occurs during the ballistic event. This requirement can be ignored if the resin in the composite ruptures at a sufficiently low strength to allow energy to dissipate during the ballistic event. Given this basic knowledge of armor design, the design of an armor laminate then becomes a tradeoff of ballistic properties of the panel against the structural requirements for the use of the panel, U.S. Pat. No. 3,000,772, Lunn, 1961, is one of the first patents to discuss the requirement for a flexible resin system for superior ballistic performance. This patent covers the use of a polyethylene film with a unidirectional glass fabric. The glass fabric has glass yarn in the warp direction and a secondary yarn in the fill direction to form the fabric. The fabric then pressed into a laminate after orienting succeeding layers of fabric at 90 degrees to the fabric layer above and below it. This is a standard practice known as “cross plying” the layers. U.S. Pat. No. 3,956,447, Denommnee, 1976, discusses the fabrication of a ballistic helmet for the US military using a thermoset or thermoplastic resin. In this patent, the preferred resin system for the helmet is a PVB/phenolic system. Roy Liable, a researcher at the US Army's Research, Engineering and Development Center in Natick, Mass., in his book, Ballistic Materials and Penetration Mechanics, Elsevier Scientific Publishing Company, 1980, page 108, discusses that, during the helmet development, it was discovered that the phenolic resin by itself was too stiff to produce good ballistic results and that the PVB component of the system was added to introduce some elongation and flexibility into the resin to improve the ballistic properties while maintaining the rigidity required of a helmet.
Several patents cover the use of thermoplastic resins and films in the composites. Lancaster et al, U.S. Pat. No. 4,678,702, 1987, teaches the use of Surlyn as the resin where a Surlyn film form flows into the woven fabric under heat and pressure to encapsulate the yarn and form flexible ballistic composite. Donavan, U.S. Pat. No. 4,574,105, 1986, teaches the use of alternating layers of nylon and Kevlar where the nylon adheres to the woven Kevlar under heat and pressure to form the composite but the nylon does not penetration the fabric. A series of patents by Andrew Park (U.S. Pat. Nos. 5,437;905; 5,443,882; 5,443,883; 5,547,536; 5,635,288; 5,935,678) covers the use of films between the layers of unidirectional yarn where the film is used to hold cross-plied layers of the yarn together without substantially penetrating the layers. Allied-Signal, U.S. Pat. No. 4,623,514, cover the substantial encapsulation of high performance yarns in cross-plied layers of unidirectional yarns with a resin with modulus less than 6000 psi.